Mosaic Bovine Viral Diarrhea Virus Antigens Elicit Cross-Protective Immunity in Calves.

Bovine Viral Diarrhea Virus (BVDV) is an important pathogen that plays a significant role in initiating Bovine Respiratory Disease Complex (BRDC) in cattle. The disease causes multi-billion dollar losses globally due to high calf mortality and increased morbidity leading to heavy use of antibiotics. Current commercial vaccines provide limited cross-protection with several drawbacks such as safety, immunosuppression, potential reversion to virulence, and induction of neonatal pancytopenia. This study evaluates two prototype vaccines containing multiple rationally designed recombinant mosaic BVDV antigens for their potential to confer cross-protection against diverse BVDV strains. Genes encoding three novel mosaic antigens, designated E2123, NS2-31, and NS2-32, were designed in silico and expressed in mammalian cells for the formulation of a prototype protein-based vaccine. The mosaic antigens contain highly conserved protective epitopes from BVDV-1a, -1b, and -2, and included unique neutralizing epitopes from disparate strains to broaden coverage. We tested immunogenicity and protective efficacy of Expi293TM-expressed mosaic antigens (293F-E2123, 293F-NS2-31, and 293F-NS2-32), and baculovirus-expressed E2123 (Bac-E2123) mosaic antigen in calves. The Expi293TM-expressed antigen cocktail induced robust BVDV-specific cross-reactive IFN-γ responses, broadly neutralizing antibodies, and following challenge with a BVDV-1b strain, the calves had significantly (p < 0.05) reduced viremia and clinical BVD disease compared to the calves vaccinated with a commercial killed vaccine. The Bac-E2123 antigen was not as effective as the Expi293TM-expressed antigen cocktail, but it protected calves from BVD disease better than the commercial killed vaccine. The findings support feasibility for development of a broadly protective subunit BVDV vaccine for safe and effective management of BRD.

Evaluation of essential oils and a prebiotic for newborn dairy calves.

A blend of essential oils (EO) and a prebiotic were combined (EOC) to formulate a colostrum-based liquid birth supplement and a separate feeding supplement (Start Strong and Stay Strong, Ralco Inc., Marshall, MN). These products were designed to promote immunity and stimulate appetite to diminish health challenges and stresses experienced by newborn calves. The hypothesis was that calves supplemented with an oral dose of liquid EOC at birth (10-mL aliquot at birth and 10 mL at 12 h of age) when fed the EOC feeding supplement would result in improved growth performance, health, and immunity. The objective was to determine if an additional feeding of liquid EOC at birth in combination with EOC in the milk replacer (MR) would allow calves to demonstrate improved growth, health, and immunity compare with calves only offered EO in MR. Sixty-one Holstein calves (18 males and 43 females) from a commercial dairy operation were blocked by birth date and randomly assigned to 1 of 3 treatments. Treatments were 1) Control (CON): a 24% crude protein (CP):20% fat (as-fed basis) MR; 2) EP: a 24:20 MR with EOC mixed at 1.25 g/d; or 3) EPC: a 24:20 MR with EOC mixed at 1.25 g/d in addition to calves receiving one 10-mL oral dose of liquid EOC at birth and 10 mL again at 12 h. The 24:20 MR was fed via bucket 2 times per day at a rate of 0.57 kg/calf daily for 14 d, increased to 0.85 kg/calf at 2 times per day until 35 d and was reduced to 0.43 kg at 1 time per day at 36 d to facilitate weaning after 42 d. Decoquinate was added to the MR at 41.6 mg/kg for coccidiosis control. Calves were housed in individual hutches bedded with straw with ad libitum access to a 20% CP-pelleted calf starter and water. All data were analyzed using PROC MIXED as a randomized complete block design. Calves in this study had similar (P > 0.10) average daily gains, body weight, and growth measurements. Calves fed EPC had significantly (P < 0.05) higher IgA titers on day 0 of the trial compared with calves fed EP or CON, which was expected as calves were supplemented with liquid EOC at birth and 12 h later demonstrating an increase in immune response. The use of a liquid EOC product being administrated after birth can improve IgA titers to improve the immune status of the new born calf to fight off potential diseases and pathogens. A formulation error resulted in the EOC being fed at half the rate of the previous experiment of 2.5 g/d, which appears to be below an efficacious dosage.

Protection against bovine respiratory syncytial virus in calves vaccinated with adjuvanted modified live vaccine administered in the face of maternal antibody.

Bovine respiratory syncytial virus (BRSV) is major viral contributor to bovine respiratory disease (BRD). BRD is a major cause of morbidity and mortality in all classes of cattle but particularly young beef and dairy calves. Passive antibodies not only help protect the calf against infection, but may interfere with the immune responses following vaccination. The purpose of this study was to evaluate the efficacy of an adjuvanted modified live virus (MLV) vaccine in the presence of well-defined maternal passive immunity. Calves were vaccinated at approximately 1 month of age and challenged ~90 days later when BRSV systemic antibodies were ≤1:4. Body temperature was lower at 6 and 7 days post challenge and other clinical signs were also lower in the vaccinates. Nasal viral shed was 3-4 times lower in the vaccinated animals as measured by virus isolation and polymerase chain reaction (PCR) and peaked 5 days post challenge compared to the controls (who peaked at days 6 and 7). On day 8 following challenge, animals were necropsied, and lung lobes were scored and tested for virus by PCR and indirect fluorescent assay (IFA). There was a 25-fold reduction in PCR virus detection in vaccinates and two of the vaccinated calves' lungs were PCR negative. Only 29.4% of vaccinated calves were BRSV positive on IFA testing at necropsy, while 87.5% of control calves were BRSV positive. Vaccinated calves developed a mucosal BRSV IgA response with over 50% of the vaccinated calves having IgA prior to challenge and all vaccinated calves were positive following challenge. Additionally, vaccination stimulated the production of Interferon gamma (IFN-γ) in mononuclear cells to prime the immune system. This study established that an adjuvanted MLV vaccine could provide protection against BRSV as measured by clinical, virological, and pathological parameters while also activating both mucosal and systemic immunity.

Priming Cross-Protective Bovine Viral Diarrhea Virus-Specific Immunity Using Live-Vectored Mosaic Antigens.

Bovine viral diarrhea virus (BVDV) plays a key role in bovine respiratory disease complex, which can lead to pneumonia, diarrhea and death of calves. Current vaccines are not very effective due, in part, to immunosuppressive traits and failure to induce broad protection. There are diverse BVDV strains and thus, current vaccines contain representative genotype 1 and 2 viruses (BVDV-1 & 2) to broaden coverage. BVDV modified live virus (MLV) vaccines are superior to killed virus vaccines, but they are susceptible to neutralization and complement-mediated destruction triggered by passively acquired antibodies, thus limiting their efficacy. We generated three novel mosaic polypeptide chimeras, designated NproE2123; NS231; and NS232, which incorporate protective determinants that are highly conserved among BVDV-1a, 1b, and BVDV-2 genotypes. In addition, strain-specific protective antigens from disparate BVDV strains were included to broaden coverage. We confirmed that adenovirus constructs expressing these antigens were strongly recognized by monoclonal antibodies, polyclonal sera, and IFN-γ-secreting T cells generated against diverse BVDV strains. In a proof-of-concept efficacy study, the multi-antigen proto-type vaccine induced higher, but not significantly different, IFN-γ spot forming cells and T-cell proliferation compared to a commercial MLV vaccine. In regards to the humoral response, the prototype vaccine induced higher BVDV-1 specific neutralizing antibody titers, whereas the MLV vaccine induced higher BVDV-2 specific neutralizing antibody titers. Following BVDV type 2a (1373) challenge, calves immunized with the proto-type or the MLV vaccine had lower clinical scores compared to naïve controls. These results support the hypothesis that a broadly protective subunit vaccine can be generated using mosaic polypeptides that incorporate rationally selected and validated protective determinants from diverse BVDV strains. Furthermore, regarding biosafety of using a live vector in cattle, we showed that recombinant human adenovirus-5 was cleared within one week following intradermal inoculation.